French astronomers using the HARPS instrument on the ESO 3.6-m telescope at the La Silla Observatory in Chile have discovered nearly 500 comets around the nearby star Beta Pictoris and have found that they belong to two distinct families: old comets that have made multiple passages near the star, and younger comets that probably came from the recent breakup of one or more larger objects.

Beta Pictoris is a young star located about 63 light-years from Earth. It is only about 20 million years old and is surrounded by a huge disc of material.

For almost three decades, astronomers have seen subtle changes in the light from this star that were thought to be caused by the passage of comets in front of the star itself.

The analysis revealed the presence of two distinct families of exocomets: one family of old exocomets whose orbits are controlled by a massive planet, and another family, probably arising from the recent breakdown of one or a few bigger objects. Different families of comets also exist in our Solar System.

“For the first time a statistical study has determined the physics and orbits for a large number of exocomets. This work provides a remarkable look at the mechanisms that were at work in the Solar System just after its formation 4.5 billion years ago,” concluded Dr Kiefer, who is the first author of the paper published in the journal Nature.